The best-selling author, 54, said the new site will feature "information and activities for children, parents and carers".
Throughout April, families will also be able to access free audiobooks and eBooks of Harry Potter And The Philosopher's Stone, the first novel in the wizarding series.
‘Children deserve a bit of magic’
Rowling said: "The teachers, parents and carers working to keep children's lives as normal and happy as possible while we're all on lockdown deserve a bit of magic.
"I hope these initiatives will give children and even adults a happy distraction during their enforced stay-at-home time."
The Harry Potter At Home hub is "an online space for younger children to discover the magic of Harry Potter - either on their own, or reading and listening" with an adult.
Wizarding Wednesdays will provide "creative and craft activities, quizzes and fun things to do for parents and carers".
Audible is making the audiobook of Harry Potter And The Philosopher's Stone free, while a collaboration with digital library supplier OverDrive will allow members to borrow the first book in the series free in April.
Neil Blair, founder of Rowling's agency The Blair Partnership, said: "The Harry Potter books have always been a refuge, comfort and escape for readers, and right now we need reading for pleasure more than ever."
Full details of all the Harry Potter At Home initiatives are at www.harrypotterathome.com.